At seven minutes past one on the afternoon of Tuesday, April 23, a tweet from the AP news agency in Washington was published. It read "Breaking: Two Explosions in the White House and Barack Obama is injured." This was not true - the AP account had been hacked by a shady group of technology nerds calling themselves the Syrian Electronic Army – but within milliseconds the tweet had been noticed and flagged by trading computers on Wall Street. Programmed to scan the internet for words or phrases that might affect sharemarkets, the unthinking machines had immediately seized upon the tweet, noted the proximity of the words "Obama", "explosions" and "White House" and unleashed a torrent of trades. Within seconds, the Dow Jones had plunged 140 points and more than $200 billion of capital had been wiped out. A few minutes later the report was exposed as a hoax and the markets quickly returned to their pre-tweet levels. But, to many, the idea that one fake tweet could have such an enormous impact on the financial markets was incredible. Who was running Wall Street? Humans or machines? Advertisement If you thought "humans", you were woefully out of date. Over the past decade or so there has been a technological coup d'etat on the trading floor. The old "Masters of the Universe" – the Gordon Gekko types with their slicked-back hair and $5000 suits – have been superseded by unbelievably powerful computers capable of analysing vast amounts of data and buying or selling shares in the blink of an eye.
